1887

Abstract

The purposeo f this study was to determinet he accuracy of shear wave velocity measurementsm ade using the seismic<br>cone penetrometer. The general framework for the performance of this test and the evaluation of the field data is from<br>the area of geophysical exploration, and is based on the premise that the first arrival time of a shear wave can be easily<br>deciphered from field seismic wave traces. However, when seismic wave traces are not clear, it is common to pick peak<br>arrival times for the calculation of interval shear wave velocities. Many of the important aspects of wave propagation<br>which can have an influence on the peak arrival times of the shear wave such as multiples, transmission effects, and<br>attenuation, are usually not corrected for, meaning that some amount of error may be introduced into the arrival times<br>used for calculating interval shear wave velocities.<br>Since development of the seismic cone, studies have been done to address this issue. However, they focused primarily<br>on using digital signal processing techniques to obtain more accurate arrival times from clear seismic cone wave trace<br>data whose first arriving shear wave times were distinct, rather than on accounting for the case where the first arrival<br>time could not be easily deciphered from the trace. For this research, we used acoustic modeling (SH wave equation) to<br>account for transmissione ffects, multiples, reflection, refraction, and ghosts. Using the acquisition geometry and the<br>velocities estimated from several seismic cone penetrometer test sites in the San Francisco bay area, we modeled the<br>theoretical seismic wave traces. We estimated the first arrival times of the theoretical seismic traces and then computed<br>interval shear wave velocities. We then compared these velocities to the field seismic cone velocities.<br>The results indicate that seismic cone velocities can be within *5% of theoretically derived velocities when the first<br>arrival time is used. When peak arrival times are used, seismic cone velocities, are approximately 20% higher than<br>theoretical velocities in soil with increasing density, and approximately 20% lower than theoretical velocities in soils<br>with decreasing density. At interfaces where there is a change in soil type, it is recommended that seismic cone<br>velocities not be used. Confidence in the resultso btained from seismicc one penetrometer test measurementsc an be<br>greatly increasedif knowledgeo f the specific soil types is available.

Loading

Article metrics loading...

/content/papers/10.3997/2214-4609-pdb.205.1996_016
1996-04-28
2024-03-29
Loading full text...

Full text loading...

http://instance.metastore.ingenta.com/content/papers/10.3997/2214-4609-pdb.205.1996_016
Loading
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error